Duncan MacMillan’s solo play finds a joyful audience for its North American premiere at the Barrow Street Theatre

Be prepared to participate when you take your seat at Every Brilliant Thing. Also be prepared to leave that seat at some point during the performance. No need to worry — but it couldn’t hurt to come with a ready-made wedding toast and a novel you wouldn’t mind being caught with. Duncan MacMillan’s one-man play, performed by British comedian and musician Jonny Donahoe, crosses the pond for its North American premiere at the Barrow Street Theatre. Beyond the hefty contributions from the crowd that make it anything but a “one-man” endeavor, it’s difficult to describe the performance piece as a “play” in the traditional sense. From the theater’s in-the-round configuration to its star’s casual rapport with the audience, Every Brilliant Thing is far more a communal experience — bordering on group therapy — than a passively absorbed theatrical presentation. Donahoe, however, with his genuine demeanor and infectious smile, succeeds in turning a piece about the grave subject of suicide into the most joyful session you’ll ever attend. The show opens on a particularly somber note as our unnamed protagonist recalls his mother’s first suicide attempt. Besides the passing of a childhood dog, this is the seven-year-old boy’s first experience with death and the baggage that inevitably comes with it. Even so, the air in the room never sinks under the weight of this heavy load. A reenactment of his pup’s final trip to the vet may not sound like a way to lighten the mood, but the brief detour adds a mild levity and childlike innocence to a subject typically filed under “adult content.”